Polishing cushion, polishing apparatus, polishing method, and article including object polished by the polishing method

ABSTRACT

A polishing cushion for realizing a plurality of types of polishing with a single polishing apparatus. A polishing cushion according to one embodiment includes a first outer layer facing one out of a polishing member and a support member, a second outer layer facing the other out of the polishing member and the support member, an inner layer positioned between the first outer layer and the second outer layer; and a plurality of spaces formed in the second outer layer which the inner layer is able to enter. The hardness of the inner layer is lower than both of the hardness of the first outer layer and the hardness of the second outer layer.

BACKGROUND

The present disclosure relates to a polishing cushion, a polishingapparatus, a polishing method, and an article including an objectpolished by the polishing method.

Polishing apparatuses for polishing metal materials or the like areconventionally known. For example, polishing apparatuses provided with apolishing disk or a polishing wheel are in common use. UK UnexaminedPatent Application Publication No. 813963 describes a contact elementfor supporting a polishing belt and applying the polishing belt onto awork piece. This contact element has a series of ridged sections with aserrated shape and a material which is softer than the ridged sectionsis packed into grooves separating the individual ridged sections. U.S.Pat. No. 7,824,248 describes a driving apparatus for an orbital sanderwhich, by eccentrically moving a drive shaft, which is eccentric withrespect to a rotating shaft extending from a driving source provided ina driving section and of which one end is rotatably coupled with therotating shaft, around the shaft core of the rotating shaft inproportion to the rotation of the rotating shaft, causes a base plate,which is supported on the driving section via a support pillar formed ofan elastic member and fixed to the other end of the drive shaft, to makean orbital motion.

SUMMARY

It is useful to be able to perform various types of polishing with asingle polishing apparatus (in other words, for example, with onepolishing disk or endless polishing belt). For example, it is useful tobe also able to intensively polish a workpiece surface by pressing apolishing surface onto an object with a relatively high pressure and, atthe same time, to finely finish the workpiece surface by pressing thepolishing surface onto the object with a relatively low pressure. Inorder to realize a broad range of types of polishing with one singlepolishing apparatus, disposing a cushioning material on a rear side ofthe polishing surface may be considered. However, it is difficult toobtain a desired polishing effect simply by adopting the conventionallyavailable cushioning materials. Therefore, there is a demand to realizea plurality of types of polishing with a single polishing apparatus asdescribed above.

A polishing cushion according to one aspect of the present inventionincludes: a first outer layer facing one out of a polishing member and asupport member; a second outer layer facing the other out of thepolishing member and the support member; an inner layer positionedbetween the first outer layer and the second outer layer; and aplurality of spaces formed in the second outer layer which the innerlayer is able to enter, wherein a hardness of the inner layer is lowerthan both of the hardness of the first outer layer and the hardness ofthe second outer layer.

In this aspect, when pressure is applied to the polishing member duringpolishing, a part of the soft inner layer enters the spaces due to thepressure. In a case where the polishing member is applied to the objectat a pressure of a degree at which the spaces are not entirely packedwith the inner layer (that is, at a relatively low pressure), it ispossible to finely finish the surface by lightly applying the polishingmember to the workpiece surface since the inner layer acts as a bufferfor the pressure. On the other hand, in a case where the polishingmember is applied to the object at a pressure of a degree at which theindividual spaces are packed with the inner layer (that is, at arelatively strong pressure), the workpiece surface is intensivelypolished by transferring almost all of the pressure to the polishingmember since the inner layer is almost completely crushed andsubstantially does not act as a buffer for the pressure. In this manner,it is possible to realize a plurality of types of polishing with asingle polishing apparatus by providing spaces into which the soft innerlayer enters in the outer layer.

According to one aspect of the present invention, it is possible torealize a plurality of types of polishing with a single polishingapparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective diagram of a polishing cushion according to anembodiment.

FIG. 2 is an exploded perspective diagram which shows an example of thepolishing cushion according to the embodiment.

FIG. 3 is an exploded perspective diagram which shows another example ofthe polishing cushion according to the embodiment.

FIG. 4 is a perspective diagram which shows still another example ofspaces in the polishing cushion.

FIG. 5 is a perspective diagram which shows yet another example ofspaces in the polishing cushion.

FIG. 6 is a perspective diagram which shows yet another example ofspaces in the polishing cushion.

FIG. 7 is a perspective diagram which shows yet another example ofspaces in the polishing cushion.

FIG. 8 is a perspective diagram which shows yet another example ofspaces in the polishing cushion.

FIG. 9 is a perspective diagram which shows yet another example ofspaces in the polishing cushion.

FIG. 10 is a perspective diagram which shows yet another example ofspaces in the polishing cushion.

FIG. 11 is a diagram of a portable grinder provided with the polishingcushion according to the embodiment.

FIG. 12 is an exploded perspective diagram which shows attachment of thepolishing cushion in the portable grinder.

FIG. 13 is a perspective diagram of a polishing wheel provided with thepolishing cushion according to the embodiment.

FIG. 14 is exploded perspective diagram which shows attachment of thepolishing cushion in the polishing wheel.

FIG. 15 is a diagram of a single action sander provided with thepolishing cushion according to the embodiment.

FIG. 16 is a diagram of a double action sander provided with thepolishing cushion according to the embodiment.

FIG. 17 is an exploded perspective diagram which shows attachment of thepolishing cushion in the single action sander or the double actionsander.

FIG. 18 is a cross sectional diagram which schematically shows stateswhere the polishing cushion according to the embodiment is changed bybeing pressed.

FIG. 19 is a table which shows the results of polishing amounts andsurface finishing in a working example and a comparative example.

DETAILED DESCRIPTION

Embodiments of the present invention will now be described in detailwith reference to the attached drawings. In the description of thedrawings, identical or equivalent elements are labeled with the samesymbols and not repeatedly described.

First, a structure of a polishing cushion 10 according to an embodimentwill be described using FIGS. 1 to 10. The polishing cushion 10 is anarticle disposed between a polishing member and a support member whichare constituent components of the polishing apparatus. In general, thenumber of purposes of the polishing is not limited to one and examplesof purposes include various types of polishing such as greatly shavingaway a surface of an object (a workpiece surface) and finely finishingthe surface. The polishing cushion 10 is used for realizing a pluralityof types of polishing with a single polishing apparatus.

Note herein that the term “polishing” in the present specification is aconcept which also includes grinding. Furthermore, the term “polishingmember” in the present specification is a component which has apolishing surface which contacts a surface of the object. In addition,the term “support member” in the present specification is a componentwhich directly or indirectly supports the polishing member and thepolishing cushion 10 during polishing.

The polishing cushion 10 as shown in FIG. 1 includes at least threelayers. Specifically, the polishing cushion 10 includes a first outerlayer 11 facing one out of the polishing member and the support member,a second outer layer 12 facing the other out of the polishing member andthe support member, and an inner layer 13 positioned between these twoouter layers. The first outer layer 11, the second outer layer 12, andthe inner layer 13 are all flat and these three layers are stacked usingan adhesive. The thickness of each of the layers may be determined inconsideration of the dimensions of the polishing member, the type anddimensions of the polishing apparatus, and the like.

The first outer layer 11 and the second outer layer 12 are manufactured,for example, with natural rubber or synthetic rubber (for example,urethane rubber or chloroprene rubber) as a main raw material. On theother hand, the inner layer 13 is, for example, a foam body obtainedfrom natural rubber or synthetic rubber. A closed cell foam is morepreferable than an open cell foam as the foam body in consideration ofthe buffering property and the elasticity of the inner layer 13.However, an open cell foam type of foam body may of course be used.Alternatively, the main raw material of the inner layer 13 may benatural rubber or synthetic rubber with a lower hardness than those ofthe first outer layer and the second outer layer 12.

The hardness of the inner layer 13 is lower than those of both of thehardness of the first outer layer 11 and the hardness of the secondouter layer 12. The hardness of each layer is measured in accordancewith “Determination of Hardness of Vulcanized Rubber and ThermoplasticRubber (JIS K 6253 (2012 Edition))” which is a standard for measuringthe hardness of rubber. For example, when the inner layer 13 is amaterial which is so soft that the hardness is difficult to measure witha Type A durometer, the hardness of the inner layer 13 may be measuredusing a Type E durometer hardness tester. As long as the relationshipdescribed above is satisfied, the hardness of the inner layer 13 and thehardnesses of the two outer layers are not limited to any specificnumerical values. As an example, the hardnesses of the first outer layer11 and the second outer layer 12 may be 70 according to the Type Adurometer and the hardness of the inner layer 13 may be five accordingto the Type E durometer. Alternatively, the hardnesses of the firstouter layer 11 and the second outer layer 12 may be 50 according to theType A durometer and the hardness of the inner layer 13 may be tenaccording to the Type E durometer. Note that the first outer layer 11and the second outer layer 12 may differ in hardness.

A plurality of spaces 14 is formed in one (the second outer layer 12 inthe present specification) of the two outer layers. The spaces 14 may beholes (spaces with no bottoms) 14 a penetrating from one surface of thesecond outer layer 12 through the opposite surface as shown in FIG. 2.Alternatively, the spaces 14 may be recesses (bottomed spaces) 14 bformed in one surface of the second outer layer 12 as shown in FIG. 3.In all cases, the surface which has the opening sections of the spaces14 out of the surfaces of the second outer layer 12 is bonded with theinner layer 13.

In FIGS. 2 and 3, the circular spaces 14 are arranged in a staggeredmanner; however, the shapes and arrangement of the spaces 14 are notlimited thereto. Some modified examples of the spaces are shown in FIGS.4 to 10. Note that the spaces are through-holes in the modified examplesof FIGS. 4 to 9; however, the spaces may of course be recesses. Thespaces are recesses in the modified example of FIG. 10.

The spaces 14 with a triangular shape are arranged in a staggered mannerin FIG. 4 and the spaces 14 with a square shape are arranged in astaggered manner in FIG. 5. Naturally, the staggered arrangement is notessential and, for example, the spaces 14 may be arranged in a gridpattern. In FIGS. 6 to 10, the individual spaces are slits. In FIG. 6,the spaces 14 which extend along one side of the second outer layer 12are arranged in a staggered manner. In FIG. 7, the spaces 14 whichextend from along one side of the second outer layer 12 are aligned witha side orthogonal to this side. In FIG. 8, the spaces 14 which extendobliquely with respect to the outer edge of the second outer layer 12are aligned. In FIG. 9, the spaces 14 with a zigzag shape are aligned.In FIG. 10, the spaces 14 which extend obliquely with respect to theouter edge of the second outer layer 12 are arranged in a network.Naturally, the shapes of the spaces 14 are not limited these examples.For example, various shapes such as hexagons, stars, ellipses,waveforms, arcs, and fans may be considered.

The spaces 14 with different shapes may be mixed in one second outerlayer 12. For example, the spaces 14 with a triangular shape may bemixed with the spaces 14 with a square shape or the spaces 14 with acircular shape may be mixed with the spaces 14 with a slit shape.Furthermore, through-holes and recesses may be mixed in one second outerlayer 12. Moreover, the sizes of the individual spaces 14 in one secondouter layer 12 may be different. For example, the circular spaces 14with a diameter of 1 cm may be mixed with the circular spaces 14 with adiameter of two cm.

The ratio of the region of the spaces 14 to the entirety of the secondouter layer 12, that is, the porosity, is not limited. The porosity may,for example, be in a range of 50 to 80%. Since there may also be caseswhere the shapes or sizes of the spaces 14 in one second outer layer aredifferent, the porosity may change according to the position of theregion which is the target of the calculation. For example, the porosityin the vicinity of a peripheral section in one second outer layer 12 maypossibly be 50% whereas the porosity in the vicinity of the center maypossibly be 70%.

Next, an application example of the polishing cushion 10 will be shownusing FIGS. 11 to 14. FIGS. 11 and 12 are an example where the polishingcushion 10 is applied to a portable grinder 20. In this example, thepolishing member is a polishing disk 21 and the support member is a pad22. The polishing cushion 10 is processed to match shapes of thepolishing disk 21 and the pad 22 and a through-hole is formed in thecenter thereof. The polishing cushion 10 is detachably attached to theportable grinder 20 in the same manner as the polishing disk 21 and thepad 22. As shown in FIG. 12, a user plugs these three components into ashaft 23, which extends from the main body of the portable grinder 20,in order of the pad 22, the polishing cushion 10, and the polishing disk21. Thereafter, the user fixes the pad 22, the polishing cushion 10, andthe polishing disk 21 to the shaft 23 by tightening a nut 24 onto a malescrew which is formed at an end section of the shaft 23.

FIGS. 13 and 14 are an example where the polishing cushion 10 isattached to a polishing wheel 30. In this example, the polishing memberis an endless polishing belt 31 and the support member is a wheel 32.FIG. 14 shows a plurality of the polishing cushions 10 shorter than theouter circumference of the wheel 32 (for example, eight polishingcushions 10 whose length is ⅛ of the outer circumference). However, thepolishing cushions 10 may be endless (that is, ring-shaped). Thepolishing cushion 10 is detachably attached onto the outercircumferential surface of the wheel 32. If the plurality of polishingcushions 10 are attached as shown in FIG. 14, an adhesive layer or abonding layer is further formed on the outer layer (second outer layer12 in FIG. 14) of the polishing cushion 10 facing the wheel 32. In sucha case, the user attaches the endless polishing belt 31 to the wheel 32after the polishing cushion 10 is affixed to the outer circumferentialsurface of the wheel 32. If the polishing cushion 10 is endless(ring-shaped), the user first fits the polishing cushion 10 into thewheel 32 and then attaches the endless polishing belt 31 to the wheel32.

It is also possible to apply the polishing cushion 10 to a single actionsander 40A shown in FIG. 15 or a double action sander 40B shown in FIG.16. These polishing apparatuses 40A and 40B each include a commonpolishing pad 41 shown in detail in FIG. 17. In the polishing pad 41,the polishing member is a polishing disk 42 and the support member is apad 43. The polishing cushion 10 is processed to match the shapes of thepolishing disk 42 and the pad 43. The polishing cushion 10 is detachablyattached to the single action sander 40A or the double action sander40B. As shown in FIG. 17, the user attaches the pad 43 to a shaft 44extending from the main body of the polishing apparatus 40A or 40B, thepolishing cushion 10 is affixed to the pad 43, and the polishing disk 42is affixed to the polishing cushion 10. Note that it is possible torealize the affixing using a surface fastener or an adhesive. Throughthese series of operations, the pad 43, the polishing cushion 10, andthe polishing disk 42 are fixed to the shaft 44.

Regardless of the type of polishing apparatus, the polishing cushion 10is used in two ways. As shown in FIGS. 11 to 17, one is in a method forattaching the polishing cushion 10 to the polishing apparatus such thatthe second outer layer 12 where a plurality of the spaces 14 are formedfaces the support member (the pad 22, the wheel 32, or the pad 43), andsuch that the first outer layer 11 which does not have the spaces 14faces the polishing member (the polishing disk 21, the endless polishingbelt 31, or the polishing disk 42). The other is in a method forattaching the polishing cushion 10 to the polishing apparatus such thatthe second outer layer 12 faces the polishing member and such that thefirst outer layer 11 faces the support member.

In this manner, the types of the polishing apparatus and the ways ofusing the polishing cushion are varied. In any cases, the user polishesan object using the polishing apparatus where the polishing cushion 10is arranged between the polishing member and the support member. Thepolished object is provided as it is as an article or as a part of anarticle.

When the user polishes the workpiece surface by applying the surface ofthe polishing member against the object, the inner layer 13 of thepolishing cushion 10, which is disposed between a polishing member 50and a support member 60, enters the spaces 14 which are formed in thesecond outer layer 12 as shown in FIG. 18. As shown in the middle partof FIG. 18, in a case where the user applies the polishing member 50against the object at a pressure of a degree at which the spaces 14 arenot completely packed (that is, a relatively low pressure), it ispossible to weakly apply the polishing member 50 against the workpiecesurface since the inner layer 13 acts as a buffer for this pressure andit is possible to finely finish the surface as a result. On the otherhand, as shown in the lower part of FIG. 18, in a case where the userapplies the polishing member 50 against the object at a pressure of adegree at which the spaces 14 are completely packed with the inner layer13 (that is, a relatively high pressure), the inner layer 13substantially does not act as a buffer for the pressure since the innerlayer 13 is almost completely crushed between the first outer layer 11and the second outer layer 12 and the spaces 14 are packed with theinner layer 13. As a result, it is possible to intensively polish thesurface of the object by transferring almost all of the pressure to thepolishing member 50.

Since the inner layer substantially does not change shape in thepolishing cushion which does not have spaces which the soft inner layeris able to enter, the result is that the inner layer substantially doesnot act as a buffer for the pressure. As a result, even though it ispossible to intensively polish the object, it is difficult to finelyfinish the workpiece surface. On the other hand, according to thepresent embodiment, it is possible to realize a plurality of types ofpolishing with the single polishing apparatus by providing the spaces 14which the soft inner layer 13 enters in the second outer layer 12.

As described above, a polishing cushion according to one aspect of thepresent invention includes: a first outer layer facing one out of apolishing member and a support member; a second outer layer facing theother out of the polishing member and the support member; an inner layerpositioned between the first outer layer and the second outer layer; anda plurality of spaces formed in the second outer layer which the innerlayer is able to enter, in which a hardness of the inner layer is lowerthan both of the hardness of the first outer layer and the hardness ofthe second outer layer.

Furthermore, a polishing apparatus according to one aspect of thepresent invention includes: the polishing cushion; the polishing member;and the support member described above.

Moreover, a polishing method according to one aspect of the presentinvention is a polishing method which uses the polishing apparatus andincludes: polishing an object using the polishing apparatus where apolishing cushion is arranged between the polishing member and thesupport member, in which the polishing cushion includes a first outerlayer facing one out of the polishing member and the support member; asecond outer layer facing the other out of the polishing member and thesupport member; an inner layer positioned between the first outer layerand the second outer layer; and a plurality of spaces formed in thesecond outer layer which the inner layer is able to enter, and ahardness of the inner layer is lower than both of the hardness of thefirst outer layer and the hardness of the second outer layer.

Furthermore, an article according to an aspect of the present inventionincludes an object which is polished using the polishing methoddescribed above.

In this aspect, when pressure is applied to the polishing member duringpolishing, a part of the soft inner layer enters the spaces due to thepressure. In a case where the polishing member is applied to the objectat a pressure of a degree at which the spaces are not entirely packedwith the inner layer (that is, at a relatively low pressure), it ispossible to finely finish the surface by lightly applying the polishingmember to the workpiece surface since the inner layer acts as a bufferfor the pressure. On the other hand, in a case where the polishingmember is applied to the object at a pressure of a degree at which theindividual spaces are packed with the inner layer (that is, at arelatively strong pressure), it is possible to intensively polish theworkpiece surface by transferring almost all of the pressure to thepolishing member since the inner layer is almost completely crushed andsubstantially does not act as a buffer for the pressure. In this manner,it is possible to realize a plurality of types of polishing with asingle polishing apparatus by providing spaces which the soft innerlayer enters in the outer layer.

In another aspect of the present invention, the first outer layer whichdoes not have the spaces which the inner layer is able to enter may facethe polishing member, and the second outer layer may face the supportmember. By providing no spaces in the first outer layer facing thepolishing member, it is possible to polish the workpiece surface withoutpatches since the pressure which is applied to the polishing cushion istransferred from the first outer layer to the polishing member almostuniformly.

In another aspect of the present invention, the surface of the secondouter layer where opening sections of a plurality of spaces are formedmay be bonded with the inner layer. In such a case, since nothing isinterposed between the inner layer and the opening sections, it is easyfor the inner layer to enter the spaces and it is easy to adjust thethickness of the inner layer for this part.

In another aspect of the present invention, the plurality of spaces maybe through-holes. Since it is possible to increase the volume of theinner layer which enters the spaces to the maximum by setting the spacesas through-holes, it is easy to apply a relatively low pressure to thepolishing member. Furthermore, since it is easy to form thethrough-holes in comparison with a case of forming the recesses, it ispossible to easily manufacture the polishing cushion in this respect.

EXAMPLES

While the present invention is described more specifically based on aworking example hereinafter, the present invention is not at all limitedthereto.

As the working example, a polishing cushion with three layers equivalentto the polishing cushion 10 described above was prepared. The main rawmaterial of the first outer layer and the second outer layer was achloroprene rubber and the main raw material of the inner layer was alsochloroprene rubber. In the working example, the hardnesses of both ofthe first outer layer and the second outer layer were 50 according tothe standards of the Type A durometer and the hardness of the innerlayer was five according to the standards of the Type E durometer.Furthermore, the thicknesses of the first outer layer and the secondouter layer were 2 mm and the thickness of the inner layer was 3 mm. Aplurality of spaces formed in the second outer layer were circularthrough-holes and the through-holes were lined up in a staggered manner.The porosity was set to 50 to 80%.

On the other hand, as a comparative example, a polishing cushion withtwo layers formed of one outer layer which did not have spaces(equivalent to the first outer layer 11 in the embodiment describedabove) and an inner layer was prepared. The main raw material and thehardness of each of the layers were the same as those of the comparativeexample.

The configuration apart from the polishing cushion and the polishingtarget object were common to the working example and the comparativeexample. As the polishing apparatus, a centerless polishing machine,Nisshinbo Hammond OD-2, manufactured by Hammond Roto-Finish Co., Inc. ofKalamazoo, Mich., USA was used. As a polishing belt, Trizact (trademark)363FC A35 manufactured by the 3M Company of St. Paul, Minn., USA wasadopted. The width of the polishing belt was 5.08 cm (two inches). Acarbon steel bar with a diameter of 5.08 cm (two inches) was used as thepolishing target object. The pressure during the polishing wasdetermined by a load current (amperes) from the centerless polishingmachine.

In the working example and the comparative example, the bar was polishedby the centerless polishing machine twice; once in a case where thepressure was increased (a load current of 4 amperes) and once in a casewhere the pressure was lowered (a load current of 0.5 amperes). Noteherein that the high pressure was a pressure of a degree at which thespaces inside the second outer layer are completely packed with theinner layer in the working example (refer to the lower part of FIG. 18)and that the low pressure was a pressure of a degree at which a part ofthe spaces inside the second outer layer are not packed with the innerlayer in the working example (refer to the middle part of FIG. 18). Inboth of the working example and the comparative example, the polishingtime was 1.5 seconds per 5.08 cm (two inches, that is, length equivalentto the width of the polishing belt) in the length direction of the bar.FIG. 19 shows the results of the polishing with two aspects of thepolishing amount and the surface finishing. The polishing amounts weredetermined according to the reduction amount in the diameter of the barand the finishing of the surface was determined by the surface roughness(specifically, the arithmetic mean roughness (Ra)).

The present invention has been described in detail with respect to theembodiments thereof. However, the present invention is not limited tothe embodiments described above. Various modifications may be made tothe present invention to the extent that they do not depart from thegist of the present invention.

In the embodiment described above, the polishing cushion 10 has athree-layer structure; however, the polishing cushion may have four ormore layers. However, an adhesive layer for affixing the first outerlayer to the inner layer and an adhesive layer for affixing the secondouter layer to the inner layer are not included as layers. That is, aseparate layer apart from the adhesive layer may be present between thefirst outer layer and the inner layer or between the second outer layerand the inner layer. However, it is necessary for a layer which ispresent between the outer layer where the spaces are formed and theinner layer to be thinned or softened to an extent that the layer doesnot interfere with the entry of the inner layer into the spaces.Alternatively, a separate layer may be stuck to the outer side of thefirst outer layer and a separate layer may be stuck to the outer side ofthe second outer layer.

In the embodiment described above, the spaces 14 are only formed in thesecond outer layer 12. However, the spaces into which the inner layerenters may be formed in both of the first outer layer and the secondouter layer. In such a case, the shapes, dimensions, and locations ofthe spaces may be the same in the first outer layer and the second outerlayer or may be different.

When using the polishing cushion 10, a separate member may be interposedbetween the polishing cushion 10 and the polishing member, or a separatemember may be interposed between the polishing cushion 10 and thesupport member. That is, the outer surface of the polishing cushion 10need not contact the polishing member or the support member.

REFERENCE NUMERALS

-   10 POLISHING CUSHION-   11 FIRST OUTER LAYER-   12 SECOND OUTER LAYER-   13 INNER LAYER-   14 SPACE-   14 a through-hole (SPACE)-   14 b RECESS (SPACE)-   21 POLISHING DISK (POLISHING MEMBER)-   22 PAD (SUPPORT MEMBER)-   31 ENDLESS POLISHING BELT (POLISHING MEMBER)-   32 WHEEL (SUPPORT MEMBER)-   42 POLISHING DISK (POLISHING MEMBER)-   43 PAD (SUPPORT MEMBER)-   50 POLISHING MEMBER-   60 SUPPORT MEMBER

1. A polishing cushion comprising: a first outer layer facing one of apolishing member and a support member, a second outer layer facing theother out of the polishing member and the support member; an inner layerpositioned between the first outer layer and the second outer layer; anda plurality of spaces formed in the second outer layer which the innerlayer is able to enter, wherein a hardness of the inner layer is lowerthan both of the hardness of both the first outer layer and the hardnessof the second outer layer.
 2. The polishing cushion according to claim1, wherein the second outer layer is adjacent the support member.
 3. Thepolishing cushion according to claim 2, wherein the second outer layerincludes a surface containing openings and the surface is bonded withthe inner layer.
 4. The polishing cushion according to claim 3, whereinthe plurality of spaces are through-holes.
 5. A polishing apparatuscomprising: the polishing cushion according to claim 4; the polishingmember; and the support member.
 6. A polishing method using a polishingapparatus, the method comprising: polishing an object using thepolishing apparatus where a polishing cushion is arranged between apolishing member and a support member, wherein the polishing cushionincludes a first outer layer facing one of a polishing member and asupport member, a second outer layer facing the other of the polishingmember and the support member, an inner layer positioned between thefirst outer layer and the second outer layer; and wherein the secondouter layer includes a plurality of spaces which the inner layer is ableto enter, and wherein a hardness of the inner layer is lower than bothof the hardness of the first outer layer and the hardness of the secondouter layer.
 7. An article comprising: the object which is polishedusing the polishing method according to claim 6.